The rebels struck at a terminal on the outskirts of the city of Peshawar, which runs into Pakistan's lawless tribal belt.

AFP - A convoy of NATO supply trucks driven by Pakistani drivers are seen as they prepare to cross into Afghanistan near the border town of Chaman.

"More than two dozen militants entered the terminal and planted timed devices on 12 out of a total 18 fuel tankers parked at the terminal," senior police official Imtiaz Shah told AFP.

He said 11 tankers were blown up while the device planted on one of the vehicles did not explode. The militants shot dead two guards and two drivers who resisted them, he said, adding that another driver was hurt in the attack.

"Those who attacked the terminal were all militants but we don't know yet which group they belong to," Shah said.

Another senior police official, Muhammad Ejaz, said the militants fled after blowing up the tankers.

An AFP reporter at the scene said the massive fire destroyed the 11 tankers. Empty shells from Kalashnikov rifles and human blood could be seen inside the terminal.

No group has claimed responsibility but the Taliban has claimed such attacks in the past. The bulk of supplies and equipment required by foreign troops in Afghanistan are shipped through Pakistan.

Pakistan shut its main northwestern border crossing to NATO supply vehicles for 11 days in September last year after a cross-border NATO helicopter assault killed two Pakistani soldiers.

Taliban and Al-Qaeda-linked militants frequently launch attacks across northwestern Pakistan and the lawless tribal belt on the Afghan border, which Washington has branded the most dangerous place in the world.

Under US pressure to crack down on Islamist havens on the border, Pakistan has in the past two years stepped up military operations against largely homegrown militants in the tribal regions.

Islamabad launched its most ambitious military offensive yet against Taliban militants in South Waziristan in 2009, expanding the campaign to many of the other seven semi-autonomous tribal districts along the border.

Washington says wiping out the militant threat in Pakistan's semi-autonomous tribal belt is vital to winning the war against the Taliban in Afghanistan and defeating Al-Qaeda.